During an appearance on Charlie Rose's TV interview program, Buffett said Dimon would be "terrific" and the "best person you could have in the job" if the U.S. ran into problems with its financial markets.

Geithner has said he plans to step down so he can return to his family in New York.

In an interview with CNBC in August 2011, Dimon said he has no interest in the job. "If you know me at all, I am not suited for politics. Anyone who runs a company and gets out in the field would say the same things I do."

On Tuesday morning, he was live on NBC's Today, where he again said raising tax rates for some of the very richest Americans would not hurt economic growth but would "raise the morale of the middle class."

Later in the program, the Berkshire Hathaway CEO did a separate interview with Loomis at his side.